Dynamical friction-driven orbital circularisation in rotating discs: a semi-analytical description

Resonant friction on discs in galactic nuclei

We argue that resonant friction has a dramatic effect on a disc whose rotation direction is misaligned with that of its host nuclear star cluster. The disc's gravity causes gravitational perturbation of the cluster that in turn exerts a strong torque back onto the disc. We argue that this torque may be responsible for the observed disruption of the clockwise disc of young stars in the Galactic Center, and show in numerical experiments that it produces the observed features in the distribution of the stars' angular momenta. More generally, we speculate that the rotation of nuclear star clusters…

Dynamical Friction and Tidal Interactions

We discuss dynamical friction in an $N$-body system in the presence of tidal interactions caused by a distant external source. Using the distant tide approximation, we develop a perturbation scheme for the calculation of dynamical friction that takes tidal effects into account to linear order. In this initial analytic approach to the problem, we neglect the influence of tides on the distribution function of stars in the background stellar system. Our result for the dynamical friction force in the appropriate limit is in agreement with Chandrasekhar's formula in the absence of tides. We provide…

一种基于$N$体模拟的新型离散动力学摩擦估计器

A New Discrete Dynamical Friction Estimator Based on $N$-body Simulations

针对星系模拟中黑洞粒子动力学摩擦难以解析的问题，提出一种基于$N$体离散性质的次网格估计器，在GIZMO中验证其与高分辨率模拟吻合且计算成本低，并优于Chandrasekhar估计器。

Corrective effect of many-body interactions in dynamical friction

Dynamical friction is a fundamental and important phenomenon in astrophysics. The Chandrasekhar formula is a well-known analytical estimation of the effect. However, current astrophysicists have realized that the formula is not correct in some cases because of several approximations dared in the formulation and/or complex non-linearities in the real universe. For example, it has been indicated that the dynamical friction doesn't work in cored density profiles (constant density in the central region) despite that the Chandrasekhar formula predicts drag force even in the constant densities. In t…

Dynamical Friction in Nonlocal Gravity

We study dynamical friction in the Newtonian regime of nonlocal gravity (NLG), which is a classical nonlocal generalization of Einstein's theory of gravitation. The nonlocal aspect of NLG simulates dark matter. The attributes of the resulting effective dark matter are described and the main physical predictions of nonlocal gravity, which has a characteristic lengthscale of order 1 kpc, for galactic dynamics are presented. Within the framework of NLG, we derive the analogue of Chandrasekhar's formula for dynamical friction. The astrophysical implications of the results for the apparent rotation…